The present invention relates to cranes which are used for lifting and carrying heavy loads.
Many types of cranes and derricks have been proposed and used. A type of crane which has been widely manufactured has a chassis mounted on four wheels, at least two of which are driven and at least two of which are steerable. An operator's station or cab is provided on the chassis, together with a source of energy which is typically an internal combustion engine. Also mounted on the chassis is a rotatable upper works or turntable, supported on a horizontal bearing carried on the chassis. The upper works includes a boom support structure, which includes a pivot shaft or trunnions on which the boom is journalled. The boom is of telescopic construction, made of plural box sections, and the sections are selectively telescopic, as by one or more hydraulic cylinders. The turntable is rotated by a suitable drive mechanism, and a cable and winch are provided in association with the boom. The operator cab or station includes controls for driving and steering the crane, for rotating the upper works, for raising and lowering the boom, for extending and retracting the boom telescopic section or sections, and for operating the winch.
Grove U.S. Pat. No. 2,911,111 discloses a crane of the above type, in which the turntable is mounted at the front end of the chassis, with the operator's station and engine located near the longitudinal mid-portion of the chassis. Stauffer U.S. Pat. No. 3,282,441 discloses a crane of this construction in which the operator's station is at the front end, the rotatable upper works is mounted at the longitudinal middle of the crane, and an engine is mounted at the rear end. Grove U.S. Pat. No. Des. 205,031 discloses a crane of this type with an operator's cab mounted at the front, the turntable behind the cab and an engine at the rear; when the turntable is positioned so that the boom extends forwardly, it extends over the operator's cab.
A number of cranes have been proposed in which the upper works includes a cab, engine, boom support, and boom. An example is Noll et al U.S. Pat. No. 3,021,016 wherein a crawler-mounted crane has an upper works with a cab above the rotary bearing, an engine rearwardly of the cab, a boom forwardly of the cab, and a super-structure above the cab for raising and lowering the boom, as well as for providing a guide for the cable. White U.S. Pat. No. 2,774,484 is generally similar. Berby et al U.S. Pat. No. 2,374,074 discloses a derrick with a rotatable upper works having a cab in front, a boom support behind the cab, a lattice boom extending forwardly from the boom support, and a derrick structure extending above the cab for supporting the boom. Tax U.S. Pat. No. 3,517,829 is another example of this construction, as is Spaulding et al U.S. Pat. No. 3,498,473.
Other constructions which have been noted include Hamilton et al U.S. Pat. No. 3,601,169, which provides a bearing mounted above the cab structure, with the boom and boom support on an upper works mounted on this bearing, and Gorl et al U.S. Pat. No. 3,885,677, which discloses a heavy duty crane with an operators cab mounted on the chassis, the chassis having a flat deck structure, with a bearing for the upper works on top of the deck structure, and the upper works including a cab mounted beside the boom. Boyer U.S. Pat. No. 3,095,978 provides a truck mounted crane in which the upper works includes an operator's seat, which is laterally offset, there being a lattice-type boom which is non-extensible, a movable support for the base of the boom on the upper works, and an upstanding A-frame structure.
The industrial cranes heretofore provided have required a relatively great height, due to the necessity of positioning the bearing for the upper works at a relatively high level, and the cranes of this type have had the operator's station or cab mounted on the chassis. Consequently, when the upper works has been rotated, the operator has not always been in position to view the load and the area around the load, so as to avoid striking a building or other object with the load, as the load is rotated. Such cranes have, also, been deficient in not providing a flat deck, which would enable loads to be carried directly on the deck.
The derrick type cranes, while providing a cab on the upper works, have required a super-structure or A-frame, for supporting the boom and/or the boom lifting apparatus, and this has resulted in an increase in the height of the structure beyond that which is desirable for industrial type cranes, which are required to operate in some locations having overhead wires or the like which will be interferred with by an exceedingly great height of the crane superstructure. Where mobile cranes have been provided with rotatable upper works including a crane cab, the crane cab has been placed beside the boom, and not beneath the boom, and thereby there has been a resulting obstruction of vision of the operator to one side when the boom is in a lowered position.